CHRONOSTRATIGRAPHY, SEQUENCE STRATIGRAPHY, AND BIOSTRATIGRAPHY OF THE PENNSYLVANIAN-PERMIAN BOUNDARY AND WOLFCAMPIAN (LOWER PERMIAN) IN MIDCONTINENT AND SOUTHWEST NORTH AMERICA

The chronostratigraphy, sequence stratigraphy, and biostratigraphy of the new Pennsylvanian-Permian boundary and Lower Permian Wolfcampian stage are correlated through Midcontinent and Southwest North America. Conodont-based correlation of the new Eurasian Carboniferous-Permian boundary stratotype to Midcontinent North America shifted the American boundary upsection significantly. The new systemic boundary and glacioeustatic sequence stratigraphy are best-documented in Midcontinent cyclothemic sections. In the Southwest's Permian basin, the systemic boundary is near a regional unconformity representing a maximum Late Paleozoic glacioeustatic lowstand and a tectonic pulse from the Gondwanan-Laurussian paleocontinental collision along the southern basin margin. In the Glass Mountains Wolfcampian stratotype, and Hueco Mountains lectostratotype, there is an angular unconformity at the systemic boundary. The Wolfcampian stratotype consists of two unconformity-bound units, the Neal Ranch Formation (Nealian substage) and Lenox Hills Formation (Lenoxian substage). The Neal Ranch-Lenox Hills unconformity is also the result of both glacioeustatic lowstand and a regional tectonic pulse, and correlates to a regional mid-Wolfcamp unconformity in the Permian basin. The top Wolfcampian unconformity is glacioeustatic in origin and is overlain by early Leonardian transgressive strata. The three major Wolfcampian unconformities of the Southwest are also reflected in the lithostratigraphy, sequence stratigraphy, and biostratigraphy of the Midcontinent, but without the tectonism and major unconformities. Global Permian stage boundary correlations are based on conodont biostratigraphy, but correlations within North America are more commonly based on fusulinids. More integrated studies of multidiscipinary biostratigraphic data and geochemical data are needed to better correlate Upper Pennsylvanian-Lower Permian strata of Midcontinent cyclothemic sections, Southwestern shelfal carbonate and basinal shale sections, and global chronostratigraphy and geologic events.